Fiber laser devices are used in the fields of processing machinery, medical equipment, measurement instruments, and the like, and light that is amplified by amplification optical fibers is output from the fiber laser devices. In such a fiber laser device, there are cases where light that is output from the core of the amplification optical fiber is input to the core of a delivery fiber, and propagates through the delivery fiber. After reaching a desired location, the light is output.
However, at the connecting portion between the amplification optical fiber and the delivery fiber, part of the light that is output from the amplification optical fiber might leak into the clad of the delivery fiber and propagate through the clad of the delivery fiber, due to axis misalignment between the cores, angle mismatch between the cores, a mode field difference between the cores, or the like. In that case, the leak light propagating through the clad is absorbed by the coating layer of the delivery fiber, and the coating layer might burn out.
Patent Document 1 listed below discloses an optical component that releases, from an optical fiber, leak light propagating through such a clad. In this optical component, the optical fiber is inserted into a glass tube that has a small inner diameter at one end and has a large inner diameter at the other end. The inner wall of the glass tube at the one end is welded to the clad of the optical fiber, and the inner wall of the glass tube at the other end is separated from the optical fiber. Leak light leaking into the clad of the optical fiber propagates from the clad to the glass tube at the welded portion at the one end of the glass tube, and the light that is input to the glass tube is released to the outside from the other end of the glass tube.